This prospective, multicentre study assessed the efficacy and safety of testosterone replacement therapy (TRT) with a long-acting intramuscular injection of testosterone undecanoate (Nebido®) in an Asian population.1 A total of 133 Korean patients (mean age 54, range 42–75 years) with erectile dysfunction (ED) and testosterone deficiency syndrome (serum testosterone <3.5 ng/mL [12 nmol/L]) were treated with testosterone undecanoate 1000 mg at baseline and again at 6 and 18 weeks. The primary efficacy endpoints were the changes in International Index of Erectile Function (IIEF) score from the initial visit to the final visit (24 weeks) and from the initial visit to each visit. Changes in the Aging Males' Symptoms (AMS) Scale and the Global Efficacy Question (GEQ) for improvement of erectile function were also evaluated.

Key Points

Serum total testosterone and free testosterone levels significantly increased by week 12 and improvements were maintained throughout the study (p<0.0001)1

Mean total testosterone improved from 2.5 ng/mL at baseline to 5.5 and 5.3 ng/ml at weeks 12 and 24, respectively

There was a tendency for serum glucose levels to improve with treatment, reaching statistical significance in men with elevated initial glucose levels1

Serum prostate-specific antigen (PSA), haematocrit and haemoglobin increased significantly at week 24, but remained within the normal range1

Only mild adverse events were observed and there were no local side effects at the injection site. No serious adverse reactions were observed.1

What is known

A variety of delivery methods of testosterone therapy have been developed, including oral preparations, transdermal gels, buccal systems, skin patches, subcutaneous implants and intramuscular injections. The formulation of 1000 mg of testosterone undecanoate in an oily vehicle (castor oil) provides a safe and well-tolerated long-acting intramuscular injection which has been shown to sustain stable physiological levels of testosterone with extended intervals of administration (every 10–14 weeks) in studies in Europe.2,3This is a considerable advantage over earlier injectable formulations, which required injection of testosterone every two to three weeks. However, efficacy and safety data of this long-acting testosterone undecanoate injection in Asian populations have been lacking.

What this study adds

This study showed that the testosterone undecanoate injection is effective, safe and well tolerated in Korean men with testosterone deficiency.1 Testosterone therapy effectively normalized testosterone levels and maintained a stable concentration throughout the study, while improving erectile function. As all patients in the study reported ED at the start of the study, it was expected that the sexual subscale score of the AMS would be improved more than other subscales. However, there was significant improvement in all subscale scores within 6 weeks of starting therapy, which was maintained throughout the study. Similarly, the IIEF data showed that there were significant improvements in sexual desire, intercourse satisfaction and overall satisfaction, in addition to erectile function and orgasmic function.

Beneficial effects on total cholesterol were demonstrated, and some improvements in plasma glucose control, particularly in the subgroup with baseline glucose levels ≥110 mg/dL (p=0.001 vs baseline, n=41). There was no change in body mass index (BMI) during the study, which may reflect a lower baseline BMI (25.0 kg/m2) in the Korean population than in general Caucasian populations. A longer follow-up period may have been necessary to further assess the effect of testosterone therapy on lipid profile and metabolic components in Asian men.